The present invention relates to cam phasers for reciprocating internal combustion engines for altering the phase relationship between valve motion and piston motion; more particularly, to cam phasers having a vaned, hydraulically-rotatable rotor disposed in an internally-lobed stator to form actuation chambers therebetween; and most particularly to a cam phaser wherein a stator is integrally formed with either a back plate carrying drive means or a front cover plate.
Cam phasers are well known in the automotive art as elements of systems for reducing combustion formation of nitrogen oxides (NOX), reducing emission of unburned hydrocarbons, improving fuel economy, and improving engine torque at various speeds. Typically, a cam phaser employs a first element driven in fixed relationship to the crankshaft and a second element adjacent to the first element and mounted to the end of the camshaft in either the engine head or block. A cam phaser is commonly disposed at the camshaft end opposite the engine flywheel, herein referred to as the xe2x80x9cfrontxe2x80x9d end of the engine. The first element is typically a cylindrical stator mounted onto a crankshaft-driven gear or pulley, the stator having a plurality of radially-disposed inwardly-extending spaced-apart lobes and an axial bore. The second element is a vaned rotor mounted to the end of the camshaft through the stator axial bore and having vanes disposed between the stator lobes to form actuation chambers therebetween such that limited relative rotational motion is possible between the stator and the rotor. The chambers are sealed at the rear typically by a gasket or O-ring between the stator and the back plate and at the front by a gasket or O-ring between a front cover plate and the stator.
Known cam phasers typically comprise these three basic chamber-forming elements: a stator, a rear cover plate (typically formed to include a drive pulley or sprocket), and a front cover plate. These three elements are manufactured separately, are carried in inventory as three distinct parts, and are assembled with two gaskets or O-rings as described above.
What is needed is an improved cam phaser wherein the stator is formed integrally with either the rear cover plate or the front cover plate, thereby eliminating one gasket or O-ring, reducing the total number of phaser parts, and eliminating a potential source of hydraulic leakage from the actuation chambers.
The present invention is directed to a cam phaser wherein the stator is integral with either the back plate or the front cover plate. The integral stator may be formed by any desired forming technique, such as, for example, by machining, casting, welding, or injection molding. Preferably, however, the integral stator is formed in a single molding step by powdered metal forming using powdered aluminum.
Also, the present invention provides for cap seals to be used in place of conventional sealing elements for sealing the hydraulic chambers of the cam phaser.